Chemical additives including surfactants have been added to wells in hydraulic fracturing processes to increase recovery of crude oil from subterranean hydrocarbon-containing formations. Hydraulic fracturing can be used to extend the life of an oil well by injecting high volumes of fracturing fluid into the well and pumping the fluid deep into the well at pressures sufficient to create or restore small fractures in the reservoir rock from which oil can be released. The surfactants can act to lower the interfacial tension between the fracturing fluid and the oil trapped within the fractures in the reservoir and can change the wettability of the reservoir rock.